const buf1 = Buffer.alloc(10)
console.log(buf1) // <Buffer 00 00 00 00 00 00 00 00 00 00>

const buf2 = Buffer.from('yk')
console.log(buf2) //<Buffer 79 6b>

const buf3 = Buffer.from('菌')
console.log(buf3) // <Buffer e8 8f 8c>   utf-8/16/32

const buf4 = Buffer.concat([buf2, buf3])

console.log(buf4, buf4.toString()) // <Buffer 79 6b e8 8f 8c> yk菌